Cooling system for dynamo-electric machines



Dec. 25,-1928. .6 ,6 1,696,612

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His AttoPne Patented Dec. 25, 1928.

UNITED STATES PATENT OFFICE.

CHESTER w. RICE, or SCHENECTADY, NEW YORK, ASSIGNOR T0 GENERAL RLRc'rRIcCOMPANY, A CORPORATION OF NEW YORK.

COOLING SYSTEM FOR DYNAMO-ELECTRIC MACHINES.

Application filed' October 17, 1925. Serial No. 63,153.'

My invention relates to dynamo electric machines and more particularlyto cooling systems therefor of the type in which the cooling gas iscaused to circulate in a closed path in the enclosing casing of themachine.

In such systems the cooling gas in passing over the more highly heatedparts of the machine in one part of its circuit absorbs heat andsubsequentlyin passing over other parts or over cooling devices arrangedin the casing gives up heat. Since the heat-dissipating properties of agas increases with its pressure, the greater amount of heat produced inthe machine as a result, for example, of a greater load thereon, may bedissipated by an increase in the pressure at which the gas ismaintained. However, a disadvantage appears when the pressure of thecooling gas is increased by reason of the fact that .a greater windageloss results there- 'from, which loss is independent of the load.

An object of my invention therefore is to provide an improved coolingsystem of the type referred. toinwhich the pressure of the. cooling gas'may be varied with changes in the load on the machine. I am thus ableto take advantage of the greater heat-transfer properties of the coolinggas at higher pressures at times of increased loads without sustainingthe greater windage loss incident to higher pressure during times ofnormal or subnormal load.

In carrying out my invention I may increase or decrease the pressure ofthe cooling gas inaccordance with observed changes 1n the load or I maycause the pressure of gas to be varied automatically in response to'variations in the load. Where air is used as the cooling gas, thepressure may be increased from atmospheric pressure to a pressuresomething like one and a half atmospheres. Where lighter gases are usedinvolving less windage losses, higher pressures may be usedadvantageously; for example with hydrogen, the pressure may be variedfrom atmospheric or slightly thereabove to a pressure of five to tenatmospheres.

Whether or not the actual pressure of gas in the machlne casing 1s aboveor below atmosphenc pressure 1s, however, lmmaterial to my lnvention.

In the accompanying drawlng forming a part of my application, I haveillustratedby way of example only one form of'apparatus embodying myinvention. A dynamo electric machine of the enclosed type is shown at 1,having bearings 2 for supporting the rotatlng element. Cooling gas iscirculated through the casing and over the parts of the dynamo electricmachine in any well known manner. The reservoir 3 in whlch the coolinggas is stored under pressure is connected to the casing of the dynamoelectric machine by the pipe 4 1n which is the valve 5 by means of whichthe flow of gas from the reservoir to the mach1ne is controlled. Thevalve is normally held closed by the spring 6 and is adapted to beopened by the energization of the soleno 1d 7. For withdrawing gas fromthe machine to the reservoir, I have shown the pump 8 operated by theelectric motor'9, the pump being connected to the machine by the pipe 10and to the reservoir by the pipe 11 in which is inserted the check valve12 to prevent a return flow of the gas. I have shown a switch 14 in thecircuit of the pump motor 9 for "controlling the operation of'the pumpand have shown a switch 15 in the circuit of the solenoid 7 by which'thevalve 5 is controlled. These two switches may be. manually operated inresponse to observed changes in, the load on the machine to increase thepressure of the cooling-gas when the load increases and to decrease thepressure when the load 'decreases.

lInthe apparatus now to be described I have illustrated a method bywhich the pressure of the cooling gas may be automatically varied withchanges in 108d. In this apparatus the wattmeter 18 is connected to thedynamo electric machine so as to register the load on thelmachine andthe pressure gauge 19 having a ipe connection 20 with the lower part oft e machine casing containing the usual cooling devices registers thepressure of the cooling gas therein. Arranged between the wattmeter andthe pressure gauge I have shown a long screw 21 carrying the nut 22 anddirect-connected with the shaft of an electric, motor 23. Two

pairs of spring-contacts 24 and 25 are se-l cured to. but insulated fromthe nut, the contacts 24 which form one' -pair having their free endslying on opposite sides and close to the pointer 26. of the wattmeterandthe contacts 25 which form the other pair'hav- 'ing their free endslying on opposite sides 5 armature connected in circuit with theresistances, the pointer 'of the wattmeter and the spring contacts 24associated therewith. The arrangement is such that movement of thewattmeter pointer a suificient amount to engage either contact causesthe motor to rotate in a direction to move the contact engaged away fromthe pointer. The pointer 27 of the pressure gauge and the springcontacts 25 cooperating therewith are shown connected in circuit with asource of current 32 and with the electron'iagnet 33 adapted to closeswitch 15 and with the electromagnet 34 adapted to close switch 14.

The operation of the apparatus for the automatic control of the gaspressure in accordance with the load is as follows: As suming the partsto be in the positions shown, any substantial increase in the load onthe machine causes the wattmeter pointer 26 to swing to the right andtouch the right spring contact 24. The motor armature circuit thus beingclosed, the armature and screw 21 rotate in a direction to move the nutto the right until the contact with the wattmeter pointer is broken. Ifthis movement of the nut 22 is suflicient to cause the left contactspring 25 to touch the pressure gauge pointer 27, the electromagnet 33will be energized to close the valve switch 15 35 whence additional gaswill be admitted to the machine casing from the reservoir. When thepressure in the machine has risen enough to cause the pressure gaugepointer to swing to the right sufficient to break connection with theleft contact 25, the valve switch 15 is released. In a similar mannerany substantial decrease in load causes the wattmeter pointer 26 totouch the left spring contact 24.

the screw is rotated in the opposite direction until the contact isbroken. The resulting movement of the nut 22 to the left may cause theright contact 25 to touch the pressure gauge pointer 27 thereby andclose the circuit of electromagnet 34. This closes the pump switch 14whence gas is pumped out of the machine into the reservoir until thepressure has fallen to the point Where the pressure gauge pointer 27breaks connection th the rightcontact 25. The pressure in the machinecasing obviously will be maintained substantially constant with theconstant load since variations in pressure due to any leaks in the valve6 or in the machine will be corrected automatically by the ap- This alsocloses the circuit of, 45 motor armature but reverses the direction ofthe fiow of current therethrough whereupon paratus associated with thepointer.

While I have described only one embodiment of my invention, I do notwish to be limited to the particular form shown and described, as itwill be apparent that many modifications therein may be made withoutdeparting from the scope of my invention as set forth in the appendedclaims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is 1. In combination, a dynamo electric machine comprising aclosed casing, means for circulating a cooling gas therethrough, andmeans responsive to a decrease in load on the machine for 'withdrawing aportion of the to lower the pressure in said casing.

2. Incombination, a dynamo electric machine comprising a closed casing,means for circulating a cooling gas therethrough, means pressure gaugeresponsive to an increase in the "load on the circulating a cooling gastherethrough, a gas reservoir, a connection between the reservoir andthe casing including a valve, controlling means therefor, a devicehaving-a movable contact responsive to the pressure of gas within thecasing, a load responsive device, a contact controlled thereby adaptedto engage said movable contact, and circuit connections between saidcontacts and the valve controlling means.

5. In combination, a dynamo electric machine comprising a closed casing,means for circulating a cooling gas therethrough, a gas reservoir, aconnection including a valve between the reservoir and the casing, apump connected between the casing and the reservoir, controlling meanstherefor, a pressure device having a movable contact responsive to thepressure of gas within the casing, a

chine, a contact controlled thereby and adapted to be engaged bysaidmovable contact, and circuit connections between said contacts andsaid pump controlling means.

In witness whereof, I have hereunto set my hand this 16th day ofOctober, 1925.

CHESTER W. RICE.

load responsive device connected to the ma-

